“Lately I feel like I’m losing more hair.” “My hairline might be receding.” — Many people share these worries. However, hair loss isn’t always caused by AGA (androgenetic alopecia); lifestyle factors, stress, and other medical conditions can also play a role. What matters is accurately understanding whether your condition stems from AGA, and deciding promptly whether you should start treatment.
This article explains, in clear and professional terms, the key points for determining whether AGA treatment is necessary.

1. Understand the Characteristics of AGA

AGA (Androgenetic Alopecia) is a progressive form of hair loss in which androgens, especially dihydrotestosterone (DHT), cause hair shafts to become thinner and shorter until they eventually fall out. It commonly develops in men after puberty. It’s said that roughly 30% of Japanese men show signs by their 30s, and about half by their 50s.

1-1. Typical Patterns of Thinning

AGA progresses in characteristic patterns, generally classified as follows:

M-shaped (receding hairline type)
Recession begins at both temples, creating an “M” shape. It’s more common in younger adults (20s–30s) and, as it advances, can thin the entire frontal area.

O-shaped (vertex thinning type)
Thinning starts around the crown and gradually spreads. Because it’s hard to see at a glance, some only notice it after others point it out.

Mixed M + O type
Thinning progresses from both the hairline and the crown. This pattern is common among Japanese men. When it advances quickly, the frontal and crown areas connect, resulting in extensive hair loss.

1-2. “Miniaturization” of Hair

AGA’s hallmark is progressive “miniaturization”—hairs become thinner and shorter over time.
Normally, hair repeats a cycle of growth (2–6 years), catagen (about 2 weeks), and telogen (3–4 months). In AGA, DHT shortens the growth phase drastically, so hairs that should grow thick and long instead fall out while still thin and short.

This leads to visible changes such as:

• Reduced overall volume
  
• Individual strands becoming finer so the scalp shows through
  
• Hairstyling becoming more difficult
  

1-3. A Progressive Condition

AGA does not improve spontaneously; it invariably progresses over time. Left unattended, the course typically looks like this:

• Subtle changes appear at the hairline and/or crown
  
• Miniaturization advances and volume declines
  
• Thick hairs dwindle; only vellus-like hairs remain
  
• Eventually follicles are lost, making treatment results harder to achieve
  

Because of this progressive nature, early detection and early treatment are critical. Starting treatment in the initial stages increases the likelihood of halting progression and promoting regrowth.

1-4. The Difficulty of Self-Diagnosis

Thinning can also result from stress, lifestyle habits, or conditions such as alopecia areata. While AGA is progressive, other types may be temporary and improve. Therefore, “more shedding ≠ automatically AGA.”
Physicians diagnose by combining family history, hair-loss pattern, and microscopic (trichoscopic) assessment of hair shafts and follicles.

2. Check the Number and Quality of Shed Hairs

2-1. Shedding Happens Even in Healthy Hair

Human hair is constantly renewing according to the hair cycle.

• Growth phase (approx. 2–6 years): Hairs grow thicker and longer; about 85–90% of scalp hairs are here.
  
• Catagen (about 2 weeks): Follicle activity wanes; growth stops.
  
• Telogen (3–4 months): Hairs shed and new hairs prepare to emerge.
  

Because this cycle repeats, shedding 50–100 hairs per day is normal. The hairs you notice in the shower or brush are just part of the total.

2-2. When the Number Becomes Concerning

Consider AGA if:

• You feel you shed 200+ hairs per day.
  For example, the drain clogs quickly after shampooing, or hairs are clearly visible on your pillow daily.
  
• Increased shedding persists for several months.
  Seasonal shedding (often in fall) usually subsides within a few weeks; longer persistence raises suspicion for AGA or other alopecias.
  

2-3. Assess the “Quality” of Shed Hairs

Beyond quantity, quality is critical to judging AGA:

• Small bulbs with many short, thin hairs
  Healthy bulbs look plump, rounded, and dark. With AGA, the growth phase shortens, producing more thin, short hairs.
  
• More fine hairs, fewer thick ones
  As overall shaft diameter shrinks, volume drops and the scalp shows more—classic miniaturization.
  
• Lighter-colored, weaker-looking hairs
  Because hairs fall before fully maturing, you may see more lighter brown, less pigmented hairs than dense black ones.
  

2-4. Miniaturization and AGA Progression

AGA fundamentally reflects DHT-driven miniaturization—DHT acts on dermal papilla cells and shortens the growth phase.

• Normal hairs: Thick, long, persisting for years
  
• Miniaturized hairs: Thin, short, shedding in months
  

Repeated cycles lead to loss of thick hairs → predominance of thin hairs → lower density → visible thinning.

2-5. Make Shedding Checks a Habit

Easy at-home methods:

• Inspect post-shampoo shed hairs in the drain: look at bulb shape and shaft thickness
  
• Line hairs up on tissue for comparison: check the ratio of thick to thin hairs
  
• Track for a week: distinguish day-to-day variance from a sustained trend
  

If you consistently notice many thin hairs and small bulbs, it’s a sign to consult a specialist.

3. Confirm Family History

3-1. AGA and Genetics

AGA is strongly influenced by genetics and androgens. DHT, converted from testosterone, acts on dermal papilla cells and impairs hair growth, driving progression.

Genetic contributors include:

• Androgen receptor (AR) gene: determines androgen sensitivity. Inherited high DHT sensitivity increases risk.
  
• 5-alpha-reductase activity: stronger conversion of testosterone to DHT promotes AGA.
  

Because these are inherited traits, family history is highly informative for risk prediction.

3-2. Which Side of the Family?

AGA risk reflects genes from both paternal and maternal lines.

Maternal influence
The AR gene lies on the X chromosome. Men inherit their X from their mother, so a maternal grandfather with baldness is associated with higher risk.

Paternal influence
A father with AGA also raises risk. Notably, similar patterns (receding hairline or vertex thinning) often recur across generations.

Siblings
If brothers develop thinning around the same age, genetic contribution is likely strong.

3-3. Patterns That Suggest Elevated Genetic Risk

Risk is higher when:

• Your father began thinning in his 30s
  
• Your maternal grandfather had vertex thinning
  
• A brother progressed to an M-shape in his late 20s
  
• Multiple male relatives share M- or O-type patterns
  

In these cases, early self-checks and specialist visits are advisable.

3-4. Interaction with Non-Genetic Factors

Genetics doesn’t make AGA inevitable. Lifestyle and environment can influence onset and progression:

• Sleep deprivation or stress
  
• Poor nutrition
  
• Excess alcohol or smoking
  
• Poor scalp condition
  

In at-risk individuals, these can trigger earlier onset or faster progression. Conversely, healthy habits may slow progression to some extent.

3-5. Why Family History Matters

Family history helps distinguish temporary shedding from progressive, inherited thinning.
If, for example, your father thinned at your current age, or your maternal grandfather thinned from the crown and you’re seeing the same, treat it as an early warning for AGA. With family history, it’s important to “consider treatment as soon as you notice signs.”

4. Consider Age and Onset Timing

4-1. Typical Ages of Onset

While AGA is common across men, age at onset influences speed and treatment responsiveness.

Late teens–early 20s
Some notice recession or vertex thinning while still students. Earlier onset correlates with faster progression, and by the early 30s thinning can become conspicuous if untreated.

Late 20s–30s
The most common onset period. About 30% of Japanese men notice signs by their 30s. Work-related stress and lifestyle shifts can accelerate progression.

40s and beyond
Androgen effects compound and thinning progresses. However, sudden worsening after 40 may point to causes other than AGA (thyroid disease, diabetes, autoimmune conditions, chronic nutritional deficits), warranting thorough evaluation.

50s–60s
More than half of men recognize AGA-related thinning. With age, follicular function declines, making results harder to achieve—underscoring early treatment’s value.

4-2. Onset Age vs. Speed of Progression

Studies indicate younger onset → faster progression:

• Teens/early 20s: rapid progression; noticeable thinning within a few years
  
• 30s: more gradual course
  
• 40s+: slower progression, but comorbid factors may contribute
  

Thus, if you’re young and concerned, earlier treatment offers a better chance to curb progression.

4-3. Conditions to Differentiate from AGA

If shedding accelerates in your 40s or if thinning is diffuse, consider other causes:

• Thyroid disorders (hypo-/hyperthyroidism) — can cause diffuse shedding
  
• Autoimmune disease (e.g., alopecia areata) — rapid, patchy hair loss
  
• Lifestyle issues — sleep deficit, iron/zinc deficiency, high stress → diffuse alopecia
  
• Drug-induced alopecia — e.g., chemotherapy, some antihypertensives, antidepressants
  

Age and onset timing are key to deciding AGA vs. other causes.

4-4. Age-Based Guidance on When to Start Treatment

Teens–early 20s:
With family history and early hairline changes, see a specialist promptly. Early treatment is particularly effective.

Late 20s–30s:
Progression often becomes noticeable. Intervene early to avoid diminishing returns.

40s+:
Use lab tests and clinical evaluation to distinguish AGA from other causes, then decide on therapy.

5. Self-Check: Criteria for Deciding Whether Treatment Is Needed

AGA is progressive; “wait and see” is the riskiest approach. Since not all shedding is AGA, use a structured self-check to decide whether to consult a specialist. Details below:

5-1. Increased Shedding

Normal daily shedding is 50–100 hairs. Be cautious if:

• You clearly shed 200+ hairs/day
  
• Shower drains clog quickly
  
• Hairs are noticeable on your pillow or desk daily
  

Consistent findings suggest shortened growth phase and a disrupted cycle, often seen in AGA.

5-2. Finer Hair and Less Volume

With AGA’s miniaturization, hair becomes progressively finer and softer:

• Hairstyles don’t hold
  
• Styling products fail to create volume
  
• The scalp shows through more easily
  

These signal early AGA progression.

5-3. More Visible Scalp at Hairline/Crown

AGA’s signature patterns:

• M-type: receding frontal hairline
  
• O-type: vertex thinning
  
• M + O: both areas
  

If lighting or photos reveal “more visible scalp than before,” consider early intervention.

5-4. Family Members with Thinning

AGA has a strong genetic component:

• Father or maternal grandfather with thinning
  
• Siblings with similar M- or O-type patterns
  

With such a history, similar progression is likely. Because genetics can’t be “prevented,” early recognition and treatment are the most effective countermeasures.

5-5. Symptoms Persist for 6+ Months

Seasonal shedding (fall/spring) typically resolves within weeks to a month.
Stress- or illness-related shedding tends to improve within a few months.
If no improvement for 6+ months, AGA is more likely.

5-6. How to Interpret Results

• 1–2 boxes checked: may be temporary shedding → monitor
  
• 3–4 boxes checked: higher likelihood of AGA → consult a specialist
  
• All 5 checked: very likely progressive AGA → seek treatment promptly
  

6. What to Confirm in a Physician’s Evaluation

Self-diagnosis can’t confirm AGA. Many conditions mimic it. A dermatology or AGA clinic evaluation determines whether it’s truly AGA and rules out other illnesses.

6-1. Visual Exam & Medical Interview (Basics)

Physicians check:

• Pattern of hair loss: M, O, or both
  
• Stage of progression: often using the Hamilton–Norwood classification
  
• History & lifestyle: family history, diet, sleep, stress, current medications, etc., to identify non-AGA contributors
  

Key point: not just “you’re thinning,” but how it’s progressing over time.

6-2. Microscopic (Trichoscopic) Assessment

Using a magnified scope to assess scalp and follicles:

• Thickness/length distribution: ratio of thick to thin hairs to detect miniaturization
  
• Follicular units: healthy units often have 2–3 hairs; AGA shifts to single-hair units
  
• Scalp condition: excess sebum or inflammation that can influence progression
  

This visualizes micro-level changes invisible at home.

6-3. Blood Tests (Differential Diagnosis)

These don’t “prove” AGA directly, but rule out other causes:

• Thyroid hormones: dysfunction can cause diffuse shedding
  
• Ferritin/iron: iron-deficiency anemia impairs hair growth
  
• Hormone panel (testosterone, DHT, estrogens): checks endocrine abnormalities
  
• Liver/kidney function: important for safely prescribing finasteride, dutasteride, minoxidil
  

Especially important in sudden progression or patients 40+.

6-4. Additional Tests as Needed

Some clinics may add:

• Genetic testing: estimates AGA risk and potential drug responsiveness
  
• Serial photography: track progression and treatment response over time
  
• Growth metrics: hair shaft diameter and growth rate to quantify miniaturization
  

6-5. Physician’s Overall Judgement

Doctors synthesize:

1. Whether the pattern fits AGA
   
2. Whether other diseases could explain the loss
   
3. Current stage and future risk
   
4. Whether to start treatment or monitor
   
5. Whether treatment can begin safely
   

They then propose the optimal treatment plan.

7. When to Start Treatment

AGA doesn’t resolve on its own; early treatment is key. Start sooner if:

• You’re in your 20s–30s and thinning is progressing
  
• Family history is present with a similar pattern
  
• You have symptoms with no improvement for 6+ months
  

Delaying invites follicle loss, reducing treatment efficacy.

8. Treatment Options

Major categories include:

Oral medications

• Finasteride, dutasteride: suppress progression
  
• Minoxidil: promotes regrowth
  

Topical medications

• Topical minoxidil: direct scalp action
  

Regenerative/Injectable therapies

• Treatments using growth factors or stem-cell–related approaches
  

Hair transplantation

• Autologous hair transplantation for lasting restoration
  

Choose based on age, stage, goals, and cost, with professional guidance.

9. Cases Where Treatment May Not Be Necessary

Not all thinning is AGA. Many cases stem from temporary lifestyle or hormonal shifts and can improve with time and habits. Key examples:

9-1. Stress- or Diet-Related Temporary Shedding

Cause: severe psychological stress or rapid dietary restriction (especially low carbs/protein) suppresses matrix cell division, increasing telogen hairs.
Features:

• Shedding increases weeks to months after the trigger (telogen effluvium)
  
• Diffuse volume reduction
  
• Thinning is evenly distributed, not localized
  Improvement: alleviating stress, balanced diet, and rest often bring recovery within 6 months.
  

9-2. Postpartum Hair Loss (Postpartum Telogen Effluvium)

Cause: after birth, pregnancy-elevated estrogen drops sharply, increasing hairs entering telogen.
Features:

• Shedding 2–3 months postpartum
  
• Notable around the hairline/temples
  
• Typically self-limited, with recovery within a year
  Improvement: no special treatment usually required; regular routines and nutrition support recovery.
  

9-3. Nutritional or Sleep Deficiency

Cause: hair is protein (keratin). Deficits in protein, iron, zinc, or vitamins, plus poor sleep (less growth hormone), impair growth.
Features:

• Finer, weaker hairs
  
• Small bulbs; hairs shed mid-growth
  
• Often accompanied by fatigue or malaise
  Improvement: balanced diet, adequate sleep, and limiting alcohol/smoking.
  

9-4. Seasonal Shedding

Cause: temporary telogen shift in specific seasons (often autumn).
Features:

• Recurs the same time each year
  
• Settles within weeks
  Improvement: routine hygiene and lifestyle; treatment typically unnecessary.
  

9-5. Drug-Induced Alopecia

Cause: chemotherapy, anticoagulants, certain antihypertensives or antidepressants.
Features:

• Marked shedding after drug initiation
  
• May involve body hair as well
  Improvement: often reverses after cessation—never stop medication without medical advice.
  

9-6. How to Tell It’s Not AGA

AGA is progressive. Temporary shedding typically shows:

• Improvement over weeks to months
  
• Uniform thinning rather than M- or O-type patterns
  
• Reduction of shedding with lifestyle/health improvement
  

Summary: How to Determine Whether You Need AGA Treatment

AGA is progressive and won’t resolve on its own. If neglected, thinning spreads and follicle loss limits future results. Early detection and treatment are the only reliable strategies to preserve future hair.

Key Checkpoints Recap

To judge whether it’s AGA, assess:

• Quality and quantity of shed hair: more thin, short hairs?
  
• Hairline/crown changes: M- or O-type progression?
  
• Family history: father/maternal grandfather/siblings with similar patterns?
  
• Age/onset: earlier onset demands more vigilance
  
• Duration: no improvement ≥6 months suggests progression
  

If multiple factors apply, consult a physician rather than self-managing.

The Next Step After Self-Check

Self-checks are guides to understand your status. If you’re uneasy, act now to avoid missing the window to slow progression:

1. Consult a specialist: dermatology/AGA clinic for visual exam, trichoscopy, and labs
   
2. Don’t delay treatment: early use of finasteride, dutasteride, minoxidil is more effective
   
3. Optimize lifestyle: nutrition, sleep, and stress control enhance outcomes
   

Early Action Protects Your Future Hair

The biggest key is to act as soon as you notice changes.

• Earlier starters are more likely to maintain hair quantity and quality
  
• The longer you wait, the more follicular function is lost—and improvement becomes harder
  

Bottom line: AGA won’t self-resolve. Perform a self-check, and if concerned, consult a specialist promptly. This simple step is your strongest tool to protect your hair’s future.
Take the first step today.

記事の監修者

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岡 博史 先生

CAPラボディレクター

慶應義塾大学 医学部 卒業

医学博士

医師